Tensioning devices for tensioning flexible drive means, especially those used in the case of timing drives of internal combustion engines, serve to maintain a certain chain or belt tension which changes due to wear of the drive means and when a change of the operating condition takes place during operation. In order to maintain the tension of the flexible drive means, the tensioning element of a tensioning device is guided in a housing such that it is movable relative to said housing.
Such a tensioning device comprising a tensioning element which is guided such that it is movable in the longitudinal direction is known e.g. from EP 947 731 A1. The tensioning element comprises here a tensioning piston which is arranged such that it is axially movable in a hole provided in the housing of the tensioning device and a guide shoe for guiding the drive chain of timing chain drive. The tensioning piston is provided with a mounting plate arranged on a tensioning end which is not guided in the housing, the tensioning shoe being clipped onto said mounting plate. The housing of this tensioning device has, on the side facing away from the tensioning element, a further guide section for guiding the drive chain. On the basis of this structural design it is possible to place this tensioning device between a timing chain drive and to guide the tensioned side as well as to tension the slack side of the timing chain drive.
DE 100 59 119 A1 shows a further embodiment of a tensioning element which is also applied to a tensioning piston that is guided in a housing in a longitudinally displaceable manner. The tensioning shoe has provided thereon two tongues which are formed integrally therewith and which are arranged in the longitudinal direction of the tensioning piston, said two tongues, in combination with a projection formed on the housing and a safety lock system, permitting the tensioning device to be arrested at a mounting position. The tensioning shoe and the tongues are preferably made of plastic material.
The tensioning elements and tensioning devices described at the beginning proved their worth in practical use, so did many other conventional structural designs. Especially with regard to the high number of pieces normally produced in the field of automobile industry, attempts are nevertheless continuously made to simplify the production or construction of components without restricting their functionality. Even a small reduction of costs in the production of components can, due to mass production, lead to a substantial saving of costs. Less complicated structural designs or production methods for components can, in addition, also lead to a reduction of the assembly expenditure or of the reject rate and can thus produce a further economizing effect.